how do i change my valo username?

my username on riot games used to be Izerec when i used to play league alot but after i quit and came back i found the username i have on riot client is a corny name i had on my gmail years ago as seen on the 1st pic.
i changed my username on the riot website to zzzereccc and STILL my username on the riot client is the same.
how do i fix?